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Wells Score for Pulmonary Embolism

Estimates the clinical pretest probability of pulmonary embolism to guide use of D-dimer and CT pulmonary angiography.

The Wells score for pulmonary embolism combines seven weighted clinical variables into a pretest probability that determines the diagnostic pathway. Combined with D-dimer it safely excludes PE in low-probability patients and directs high-probability patients to imaging.

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📐 Formula

Sum of weighted criteria; three-tier: <2 low, 2–6 moderate, >6 high. Two-tier: ≤4 PE unlikely, >4 PE likely.

When to Use

  • Adult patients with suspected acute pulmonary embolism (pleuritic pain, dyspnoea, haemoptysis, unexplained tachycardia).
  • Before ordering D-dimer or CT pulmonary angiography to stratify pretest probability.
  • Emergency department and inpatient assessment of possible venous thromboembolism.

How It Works

  • Assign points: clinical signs of DVT +3; PE most likely diagnosis +3; heart rate > 100 +1.5; immobilisation/surgery +1.5; prior DVT/PE +1.5; haemoptysis +1; malignancy +1.
  • Sum the points to obtain the total score.
  • Apply either the three-tier (low/moderate/high) or two-tier (unlikely/likely) interpretation.

Interpreting the Result

  • Three-tier: < 2 low probability; 2–6 moderate probability; > 6 high probability.
  • Two-tier: ≤ 4 PE unlikely; > 4 PE likely.
  • PE unlikely + negative high-sensitivity D-dimer: PE can be excluded without imaging.
  • PE likely (or positive D-dimer): proceed to CT pulmonary angiography (or V/Q if CTPA contraindicated).

Limitations & Pitfalls

  • Includes the subjective "PE most likely" item, which reduces reproducibility.
  • Not validated for pregnancy (use pregnancy-adapted algorithms) or for recurrent/known VTE on anticoagulation.
  • A low score does not exclude PE without an appropriate D-dimer strategy.

References

  • Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging. Ann Intern Med. 2001;135(2):98-107.
  • Wells PS, Anderson DR, Rodger M, et al. Derivation of a simple clinical model for PE probability (Christopher / two-tier). Thromb Haemost. 2000;83(3):416-420.

⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.